1. Field of the Invention
The present invention relates to an adhesive composition, more particularly, it relates to an adhesive composition which can be rapidly hardened at room temperature and which is suitable for an adhesive composition for wood.
2. Description of the Prior Art
Theretofore, resinous condensates or cocondensates of formaldehyde with urea, melamine, phenol, resorcinol etc, (hereinafter, referring to as condensate type resin) have been used for secondary processing to prepare plywoods, particle boards, combined substrates, construction substrates, furniture and other bonded articles.
The hardening of these condensate type resin adhesive compositions is relatively slow at room temperature and accordingly, it is usually necessary to heat it.
In the preparation of the combined substrates, furniture and the other secondary processings wherein a heat-hardening process can not be applied, it takes a long time for a compression as the hardening is too slow at room temperature whereby the productivity is remarkably limited. In order to promote the hardening at room temperature, it has been proposed to add a strong acidic material. However, the method is not preferable because of the stain or deterioration of the substances.
Sometimes, resins having high concentration degree of condensation have been used for the bonding operation at room temperature. However, these resins are not completely water soluble in water whereby it is necessary to use an organic diluent such as methanol. It is not preferable to use an organic solvent as the solvent for an adhesive composition from the viewpoints of the pollution in the working environment and the danger of fire and the public pollution.
On the other hand, the emulsions of resin such as vinyl acetate resin and epoxy resin have been used as the adhesive composition containing no organic solvent. These resins have disadvantages of relatively slow rate of hardening and inferior water resistance.